The present invention relates to a disc brake suitable for use in an automotive vehicle.
A typical disc brake includes a carrier including a pair of axially and outwardly extending arms extending over a rotor, a caliper slidably supported on the arms and extending over the rotor, a pair of inboard and outboard friction pads slidably mounted to the arms and urged into frictional engagement with opposite sides of the rotor by the caliper, and a pair of pad springs mounted to the arms and adapted to resiliently urge the inboard and outboard friction pads against the arms.
In such a disc brake, a piston disposed within the inboard side of the caliper is slid toward the rotor under the influence of hydraulic fluid when a pedal brake is depressed. The piston cooperates with the outboard side of the caliper to urge the inboard and outboard friction pads into frictional engagement with opposite sides of the rotor so as to apply a braking force thereto. When the pedal brake is released, the piston is moved back toward the inboard side of the caliper as the hydraulic fluid is no longer fed to the piston. As a result, the friction pads are separated from the rotor.
When the piston is returned to its initial position, the distance between the rotor and the friction pads is approximately half the amount of movement of the piston. Where the sliding resistance between the carrier and the friction pads is relatively large, the friction pads may remain in sliding contact with the rotor even after the pedal brake is released. This is commonly referred to as "drag" of the friction pads. Such drag brings about a reduction in fuel economy of the vehicle as well as the service life of the friction pads due to wear.
Various attempts have been made to overcome this problem. For example, Japanese laid-open utility model publication No. 56-21633 teaches the use of a wire spring which is generally V-shaped and extends over a rotor. A pair of friction pads have holes adjacent to the outer periphery of the rotor. Opposite ends of the wire spring are inserted into the holes so as to interconnect the friction pads and urge the friction pads in a direction away from each other. However, the direction in which a force is applied from the wire spring to the friction pads is inclined relative to the axis of the rotor. As such, the friction pads can not smoothly be slid on the arms of a carrier. This results in drag of the friction pads. Also, where the sliding resistance between the inboard friction pad and the corresponding arm is different from that between the outboard friction pad and the corresponding arm, these friction pads may not be separated by an equal distance from the rotor. As this occurs, one of the friction pads remains in sliding contact with the rotor, causing drag. Moreover, the use of the discrete wire spring results in an increase in the number of parts, and the formation of the holes results in an increase in the machining steps and production cost of the overall disc brake.
Japanese laid-open utility model publication No. 57-61237 discloses a disc brake wherein a pair of leaf springs or arms extend in the direction of rotation of a rotor and are inwardly bent from a pair of pad springs disposed between a pair of friction pads and a carrier. The leaf springs are contacted with confronting sides of the friction pads so as to constantly urge the friction pads in a direction away from the rotor. However, mere contact of the leaf springs with the friction pads is not sufficient to separate the friction pads from the rotor when a pedal brake is released. Also, the leaf springs extend outwardly from opposite sides of the pad spring. This requires a metal sheet of a larger width or size.
Accordingly, it is an object of the present invention to provide a disc brake which insures separation of a pair of inboard and outboard friction pads from a rotor when a pedal brake is released, which effectively eliminates the occurrence of "drag" of the friction pads, and which is economical to manufacture.